bake_probe_instance api needs to be updated
For one, this function should take an existing margo instance rather than creating one internally.
Additionally, we could probably just pass in the
hg_addr_t of the bake-bulk server we want to probe, rather than passing in an address string and looking it up. In the case of composed services (like mobject), another entity (SSG) may already have the address, saving an additional lookup.